Application of Phosphonium Ionic Liquids as Ion Carriers in Polymer Inclusion Membranes (PIMs) for Separation of Cadmium(II) and Copper(II) from Aqueous Solutions.

Beata Pospiech

doi:10.1007/s10953-015-0413-2

Abstract

Facilitated transport through polymer inclusion membranes (PIMs) is a promising method for simultaneous separation and removal of valuable and toxic metal ions from aqueous solutions. Recently, ionic liquids (ILs) have been used as extracting agents for metal ions due to their unique physicochemical properties. This paper presents research on the facilitated transport of cadmium(II) and copper(II) ions from aqueous chloride solutions through PIMs with phosphonium ILs as new selective ion carriers. Cellulose triacetate membranes containing o-nitrophenyl octyl ether (ONPOE) as a plasticizer and Cyphos IL 101 [trihexyl(tetradecyl)phosphonium chloride] or Cyphos IL 104 [trihexyl(tetradecyl)phosphonium bis(2,4,4-trimethylpentyl)phosphinate] as the ion carriers have been prepared and applied for investigations. Cd(II) ions were transported preferably from hydrochloric acid solutions containing Cu(II) ions through the PIMs. Higher selectivity coefficient of Cd(II) over Cu(II) (SCd/Cu) from 0.1 mol·dm−3 hydrochloric acid was obtained for PIM with Cyphos IL 104 as the ion carrier. The influence of HCl and NaCl concentrations in the source phase on metal ion transport across PIM doped with Cyphos 104 was studied. It was found that the initial fluxes of Cd(II) and Cu(II) increase with increasing chloride ions concentration in the source phase. The selectivity coefficient for Cd(II) over Cu(II) decreases with increasing HCl concentration in the source phase. The results suggest that the separation system presented in this paper can be useful for the removal of Cd(II) from acidic chloride solutions in the presence of Cu(II).

Highlights

Techniques for the separation of metal ions from industrial and waste solutions are extremely important in industrial applications
The phosphonium ionic liquids (ILs), such as: Cyphos IL 101 and Cyphos IL 104 have been chosen for the separation process of Cd(II) and Cu(II) because these salts differ by anions that can affect extraction properties of these ILs
Cyphos IL 101 contains a hydrophilic chloride anion, while Cyphos IL 104 is a derivative of Cyanex 272 and contains bis(2,4,4trimethylpentyl)phosphinate anion

Summary

Introduction

Techniques for the separation of metal ions from industrial and waste solutions are extremely important in industrial applications. Transport of metal ions from aqueous dilute solutions through liquid membranes was established as an alternative to other separation methods. O-nitrophenyl octylether (ONPOE) was used as plasticizer in this study because this compound shows remarkable physicochemical properties, including: a high dielectric constant, low solubility in water and low toxicity [6]. It acts as a good organic solvent for carrier molecules and improves the membranes softness and flexibility [7]. The choice of plasticizer influences the separation properties of the prepared membranes because the transport flux of metal ions depends strongly on the chemical nature of the plasticizer [8]. Kebiche-Senhadji et al [10] reported that the dielectric constant influences the balance between the efficiency of association and disassociation for the uptake of the metal ions by the ion carrier and its release from the complex metal-ion carrier at the receiving interface

Objectives

Results

Conclusion